1. Field of the Invention
This invention relates to a resistive temperature sensor for detecting a temperature in high-temperature atmospheres of automobile exhaust gases, kerosine stoves, hot plates, etc.
2. Description of the Related Art
For example, a temperature sensor for detecting high temperatures of 1000.degree. C. or more in a short time is required to be excellent in heat resistance, environmental resistance, and impact resistance and have small heat capacity. In other words, if the temperature sensor is exposed to a high-temperature environment for hours, it needs to be hard to undergo chemical change and have sufficient resistance to corrosion of corrosive gases of sulfur compounds, etc., in automobile exhaust gases and fuel combustion gases.
Hitherto, for example, a metal compound or metal having heat resistance, such as tungsten or platinum, has been used sometimes as a temperature sensing material of a temperature sensor for detecting high temperatures. A resistive temperature sensor using a thermistor made of a metal oxide in place of metal as the temperature sensing material and comprising a thermistor layer formed on a ceramic substrate is described in Unexamined Japanese Model Utility Publication No. Hei 2-45603. A resistive temperature sensor using a thermistor made of a metal and ceramic mixture and comprising a cermet layer formed on a ceramic substrate is described in Unexamined Japanese Patent Publication (kokai) No. Hei 7-190863.
To improve responsivity of the measurement result of a temperature sensor to temperatures, temperature following property need to be provided by lessening the heat capacity. The heat capacity can be lessened by reducing the shape dimensions of the temperature sensing section. However, for example, to use the temperature sensor in harsh environments of installation in an automobile, etc., the mechanical strength capable of enduring vibration and impact during the equipment operation. In addition, since the temperature sensor needs to be assembled firmly, a mechanical strength with no hitch in work is required in the assembling step.
Therefore, the temperature sensing section is formed on the ceramic substrate where it requires a reasonable size in the temperature sensor comprising the thermistor or cermet layer formed on the ceramic substrate as described above in the publication, so that there are inevitable limitations to miniaturization of the shape dimensions of the temperature sensing section and there are also limitations to reduction in the heat capacity.
As described above, in the temperature sensor using a heat-resistant metal compound or metal of tungsten or platinum, the heat-resistant metal and metal compound do not have sufficient heat resistance or environmental resistance and the surfaces are coated with heat-resistant and environmental-resistant materials; there are inevitable limitations to miniaturization of the shape dimensions of the temperature sensing section and there are also limitations to reduction in the heat capacity.
Thus, the conventional temperature sensors are hard to detect a temperature in a short time over a long term in the range of room temperatures to high temperatures of 1000.degree. C. or more.